Step 1: Preheat your oven to 375°F (190°C). Pat chicken thighs thoroughly dry with paper towels. Season generously all over with salt and black pepper.
Step 2: Heat olive oil in a large, oven-safe pot or Dutch oven over medium-high heat. Once shimmering, place chicken thighs skin-side down in the pot. Sear for 5-7 minutes until the skin is deeply golden brown and crispy. Remove chicken from the pot and set aside on a plate.
Step 3: Reduce heat to medium. Add diced onion to the pot and sauté for 3-5 minutes until softened and translucent, scraping up any browned bits from the bottom of the pot. Stir in minced garlic and cook for 1 minute until fragrant.
Step 4: Add the rinsed long-grain white rice to the pot and stir for 1-2 minutes to lightly toast it.
Step 5: Pour in the chicken broth and fresh lemon juice. Stir well, making sure to scrape up any bits stuck to the bottom of the pot. Bring the mixture to a gentle boil, then reduce the heat to low. Add the fresh rosemary and thyme sprigs.
Step 6: Return the seared chicken thighs to the pot, nestling them into the rice mixture skin-side up. Arrange lemon slices around the chicken, if using.
Step 7: Cover the pot tightly with a lid or foil. Transfer the covered pot to the preheated oven and bake for 25-30 minutes, or until the rice is tender, and the chicken is cooked through (internal temperature of 165°F or 74°C).
Step 8: Remove from the oven. Let the dish rest, covered, for 5-10 minutes before serving. This allows the flavors to meld and the rice to fully absorb any remaining liquid.
Step 9: Discard herb sprigs. Garnish with fresh parsley or extra lemon zest, if desired, and serve directly from the pot.